Racetrack Surface and Hind Limb Fetlock, Hoof Kinematics (AAEP 2012)

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Originally published on TheHorse.com

Exactly how different racing surfaces affect horses--specifically the lower portions of the legs--remains unlcear. Anecdotal evidence suggests that synthetic track surfaces could be more assciated with some musculoskeletal injuries than dirt or turf surfaces. In order to understand the interaction between surface and horse health better, a research team recently evaluated Thoroughbreds’ hind limb motion on dirt and synthetic surfaces.

Jennifer E. Symons, MS, a PhD student in Biomedical Engineering, at the University of California, Davis, J.D. Wheat Veterinary Orthopedic Research Laboratory, presented the study findings at the 2012 American Association of Equine Practitioners convention, held Dec. 1-5 in Anaheim, Calif.,

Symons and colleagues applied kinematic markers to specific points on five Thoroughbred racehorses' lower limbs before sending the animals out to gallop on a dirt surface and a synthetic surface. The team used high-speed video analysis to evaluate joint angles during workouts.

Their key findings included:

• When horses galloped on the dirt track, their hind fetlocks flexed 15° more than the when the animals worked on the synthetic track (maximum hyperextension was greater on the dirt track).
• When working on the dirt track, the horses experienced greater horizontal hoof slide--approximately 4 inches--than when breezing on the synthetic track, where hooves slid approximately 1.5 inches (i.e., hooves slid more readily a dirt track than on a synthetic track).

Symons and colleagues found that horses working on dirt surfaces similar to the study track appear to have greater forces placed on their proximal sesamoid bones and greater strain placed on their suspensory ligaments when compared to those working on the synthetic surfaces similar to the one studied. Regarding surfaces similar to those studied, horses would be more likely to injure their hind fetlock on the dirt surface than on the synthetic surface.

"Anecdotal reports suggest that the incidence of musculoskeletal injuries in the hind limbs has increased on synthetic surfaces," Symons explained. "Trainers hypothesize that these injuries are due to decreased hoof slide. The results of this study did confirm lesser hoof slide seen on synthetic surfaces. However, we currently have no data that supports a causal relationship between less hoof slide and increased injury.

"Future studies are focused on determining the ideal hoof surface interaction to reduce the incidence of injury," she concluded.

She noted that further studies are needed to help achieve the researchers ultimate goal of reducing injury incidence with different surfaces: "Ultimately, we wish to design consistent race surfaces that reduce the incidence of racehorse musculoskeletal injury," Symons concluded. "In the interim, altering horseshoe design by removing or adding traction devices like caulks or stickers may allow trainers to increase or decrease hoof slide for horses training or competing on different race surfaces," depending on trainers' personal preferences.

Disclaimer: Seek the advice of a qualified veterinarian before proceeding with any diagnosis, treatment, or therapy.

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